1. Field of the Invention
The present invention relates to a switching power supply device.
2. Description of the Related Art
Conventionally developed are switching power supply devices, including a DC/DC converter that transforms the voltage of a direct current (DC) disclosed in Japanese Patent Application Laid-open No. 2015-70716, for example. The DC/DC converter converts DC power supplied from a DC power supply into alternating-current (AC) power by an inverter and transforms the AC power by a transformer. The DC/DC converter rectifies, by a rectifier circuit, the AC power resulting from transformation to generate DC power and smooths and supplies the DC power to a load. In this case, the DC/DC converter may possibly generate surge power by leakage inductance of the transformer, for example. The DC/DC converter includes a snubber circuit to reduce the surge power to be supplied to the load. The snubber circuit, for example, stores the surge power in a capacitor, thereby reducing the surge power to be supplied to the load. If the surge power is stored in the capacitor, the snubber circuit turns on a switching element and supplies the surge power to the load. By contrast, if the surge power is not stored in the capacitor, the snubber circuit turns off the switching element and does not supply the surge power to the load.
The snubber circuit repeatedly turns on and off the switching element depending on the surge amount of the surge power, thereby intermittently operating. As a result, the snubber circuit may possibly generate noise in an audible range. Consequently, the conventional switching power supply devices still have room for improvement.